linux 32 Bit OS on a 64 Bit Processor Utilizing More Than 4GB of RAM?

[Schyken]

So, I'll preface this with some detail. I have a laptop, specifically I have the HP 2000 Notebook that came out for Windows 8 approximately 3.8 years ago. It is loaded with a 64 Bit AMD processor of some sort. I've installed a 32 bit Linux (Mint) OS onto it. My question is... Can a system running a 32-bit OS on a 64-bit processor utilize MORE than the 4GB RAM limit? I mean, I understand that it being 32-bit limits it to 4GB, but since its running on a 64-bit processor, will it be okay? I mean... the processor itself can handle larger data sets than an i386 processor... but will the OS being 32-bit hamper my master plan?

[blu4]

The limitation is the OS, not the CPU. You NEED a 64bit OS and 64bit CPU to address more than 3.8GB of RAM.

[Schyken]

2 minutes ago, blu4 said:

The limitation is the OS, not the CPU. You NEED a 64bit OS and 64bit CPU to address more than 3.8GB of RAM.

Hmm, that's a shame... I don't understand why the OS limits it... Is it because the OS doesn't have the capability of communicating that data with the CPU? Like a calculator without the multiply logic? It can do it physically, but not through software? (I only use this example because I made a few mistakes making a calculator)

[porina]

There is PAE which allows 32 bit OS to use more than 4GB if enabled. You'll have to look up what support there is, and how to enable it if so. Or just go 64 bit anyway.

[Schyken]

2 minutes ago, porina said:

There is PAE which allows 32 bit OS to use more than 4GB if enabled. You'll have to look up what support there is, and how to enable it if so. Or just go 64 bit anyway.

Just combed through my OS and found that PAE on my setup can go as high as 48GB of physical RAM and 72GB of virtual RAM. Not that I'll ever be able to go that high on this laptop due to power consumption and in general, the cpu and motherboard having support NOWHERE NEAR what I'd need to do that. I guess I'll stick with 12. Thank you to everyone who provided insight!

[vorticalbox]

 

34 minutes ago, Schyken said:

Hmm, that's a shame... I don't understand why the OS limits it... Is it because the OS doesn't have the capability of communicating that data with the CPU? Like a calculator without the multiply logic? It can do it physically, but not through software? (I only use this example because I made a few mistakes making a calculator)

its because of the addresses available to a 32 bit os limit it to 4gb.

 

64 bit os can see upto 128 GB on home with professional and Enterprise being able to see 512 GB

[Solarisfire]

Wondering how we arrive at that 4GB limit? Here's the math for 32-bit systems:

2³² = 4,294,967,296 bytes 4,294,967,296 / (1,024 x 1,024) = 4,096 MB = 4GB

It's different for 64-bit:

2⁶⁴ = 18,446,744,073,709,551,616 18,446,744,073,709,551,616 / (1,024 x 1,024) = 16EB (exabytes)

[Azgoth 2]

Why not just put a 64-bit Linux distro on it?  Then you can make full use of the 64-bit processor architecture, without needing a PAE workaround or anything like that.

[Schyken]

9 hours ago, Solarisfire said:

Wondering how we arrive at that 4GB limit? Here's the math for 32-bit systems:

2³² = 4,294,967,296 bytes 4,294,967,296 / (1,024 x 1,024) = 4,096 MB = 4GB

It's different for 64-bit:

2⁶⁴ = 18,446,744,073,709,551,616 18,446,744,073,709,551,616 / (1,024 x 1,024) = 16EB (exabytes)

Yes, I understand how the bit limit works. I just don't understand why most 32-bit OS have that cap if the physical hardware is more than adequate.

 

2 hours ago, Azgoth 2 said:

Why not just put a 64-bit Linux distro on it?  Then you can make full use of the 64-bit processor architecture, without needing a PAE workaround or anything like that.

I have a few reasons for not using a 64-it OS on it. I know that depending on processor, these results may vary. But I have been working with the architecture of the AMD E-300, and there are significant improvements in performance, efficiency, and thread handling with a 32-bit system rather than a 64-bit one. With a few tweaks, I've managed to essentially force the CPU to utilize it's full processing power over the 32-bit system. (About 1.8x the performance)

[Hamosch]

Yes, I understand how the bit limit works. I just don't understand why most 32-bit OS have that cap if the physical hardware is more than adequate.

 

It is because the Operating system implements and manages the virtual memory. The operating system manages virtual page tables that map the processes virtual memory addresses to physical memory addresses.  Therefore if the operating system is 32 bit it is only going to give programs 32 bits of virtual address space and also can only address 32 bits of physical address space.

 

Therefore even if the CPU can address more than 32 bits of physical address space the page tables never map anything there (because the OS cant address it) and therefore the CPU will only work with 4GB of memory.

 

This is why the fix for this is called PAE (physical address extension) ie the OS can address more than 32 bits of physical addresses.

[Burusutazu]

Ubuntu based distrobutions support more than 4gb on 32bit but 64bit is recommended anyways.

[Electronics Wizardy]

On 5/23/2016 at 0:11 AM, Schyken said:

So, I'll preface this with some detail. I have a laptop, specifically I have the HP 2000 Notebook that came out for Windows 8 approximately 3.8 years ago. It is loaded with a 64 Bit AMD processor of some sort. I've installed a 32 bit Linux (Mint) OS onto it. My question is... Can a system running a 32-bit OS on a 64-bit processor utilize MORE than the 4GB RAM limit? I mean, I understand that it being 32-bit limits it to 4GB, but since its running on a 64-bit processor, will it be okay? I mean... the processor itself can handle larger data sets than an i386 processor... but will the OS being 32-bit hamper my master plan?

Yes you can do it just fine because most linux distros have PAE that let you have more than 4gb of ram(64gb max i think). This was also support in some versions of windows server 2003.

[Fourthdwarf]

Just remember to upgrade to 64bit in the next 20 years, before 2038.